Digital Multimeter What is a Digital Multimeter?　Basic information and explanation of how digital multimeters differ from analog testers Digital multimeters are measuring instruments that can measure quantities such as voltage, current, and resistance. Measured values are shown on a digital display, allowing them to be read easily and directly, even by first-time users. Some digital multimeters select the measurement range automatically, eliminating the need to choose it manually. Consequently, these instruments are comparatively easy to use, even for beginners. Naturally, analog testers also offer advantages, for example in terms of the ease with which changes in the measured value during measurement can be read and the intuitive ease with which a needle can be viewed in locations where a digital reading might be difficult to see. Since both digital multimeters and analog testers have advantages, you can choose the instrument that’s best for your application by clarifying what you wish to measure. How to Use Your Digital Clamp Meter Digital clamp meters ;are great tools, whether you're an experienced professional or an amateur who’s just starting out. We think that everyone should have one in their toolbox. Inside the hard jaws of your new digital clamp meter is ferrite iron. This is what measures the magnetic field of a current as it flows through a conductor. A current transformer senses the fluctuations in the magnetic field and converts the value to an AC reading, which shows up on your display. Clamp meters are great for high AC currents, which make them an ideal tool to have around. If you're familiar with how direct currents work, you might wonder how a clamp meter would help you in a situation when you need to measure DC currents instead of AC. Clamp meters that can measure DC current use the Hall Effect to give you a correct measurement. However, digital clamp meters aren't limited to just AC/DC current measurements. Your purchase may have included extra sensors to make the tool even more versatile. If that's the case, you can plug test leads into your clamp meter to analyze things like voltage. Here's the best part — unlike old-fashioned test probes, you can use a clamp meter to get a current reading without breaking a circuit. No shutting off circuits, no cutting into wires — just clamp the meter around a wire and get your reading. Safe and convenient. What is a non-contact voltage tester?A non-contact voltage tester pen ;is an electrical tester that helps to detect the presence of voltage. Voltage presence is useful information to have when troubleshooting or working on a failed asset. The first tool you'll reach for is a non-contact voltage detector. How do non-contact voltage testers work?Non-contact voltage testers work by sensing a very small amount of current that is capacitively coupled from the live circuit to the tester and back to the ground. Non-contact voltage tester pens light up when they detect this current without needing to make direct contact. ; A built-in sensor at the tip of the tester detects the presence of voltage when touching a conductor, outlet, or supply cord. By holding the tool, you are the ground reference through capacitive coupling. When the tip glows red and the unit beeps, you know voltage is present. How to use a non-contact voltage tester To use a non-contact voltage tester pen you only need to touch the tip of the tester to the wire or, if you're testing an outlet, the tip of the tester needs to be placed on the faceplate of a smaller plug slot. Most testers will light up and/or make a sound to confirm voltage is present. In the Fluke 1AC II Non-Contact Voltage Tester, the tip glows red and a beeper sounds when voltage is detected. What Is a Socket Tester? A socket tester ;is a portable electrical instrument used to test for correct operation and wiring standards on power outlet sockets. It is typically a hand-held instrument that either plugs directly into the socket with pins mounted on the tester or come equipped with a short lead and plug. Depending on the sophistication of the socket tester, a range of status indications may be returned including disconnected phases, reversed phases, and, in the case of a top-end instrument, earth loop impedance. Most testers display test results on an array of light-emitting diodes (LEDs), and some also allow for an earth leakage test to be carried out with the push of a button. Socket testers are available for most common industrial and domestic voltages and pin configurations. A sound level meter (also called sound pressure level meter (SPL)) is used for acoustic measurements. It is commonly a hand-held instrument with a microphone. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. The diaphragm of the microphone responds to changes in air pressure caused by sound waves. That is why the instrument is sometimes referred to as a sound pressure level meter (SPL). ; Sound level meters are commonly used in noise pollution studies for the quantification of different kinds of noise, especially for industrial, environmental, mining, and aircraft noise. The current international standard that specifies sound level meter functionality and performances is the IEC 61672-1:2013. However, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. Specific loudness is a compressive nonlinearity and varies at certain levels and at certain frequencies. ; Radiation detectors ;and monitoring systems are essential for the detection and monitoring of ionizing radiation (alpha particles, beta particles, gamma rays, and X-rays) and neutrons. These systems are typically based on either direct or indirect (scintillation-based) methods of detecting radiation. Direct detection relies on the detector absorbing radiation by itself. The direct method gives better energy resolution than the indirect, but the available detectors are limited in size and can’t be used for large portal systems installed at border patrol locations, for example. Indirect detection relies on a scintillator converting the radiation to visible light for the detector to detect. Detectors used in the indirect method vary in size from small to large, so they can be integrated into systems ranging from pocket-sized personal monitors to much larger portal monitors. They also offer high sensitivity and are typically lower in cost. DC Power Supplies Information DC power supplies ;are power supplies that produce an output DC voltage. Power supplies are devices that deliver electric power to one or several loads. They generate the output power by converting an input signal into an output signal (in this case, a DC output). DC power supplies are categorized by the mechanism used to convert and transfer the input power to the output power. There are three main categories: Linear power supplies accept AC inputs and provide one or more DC outputs for a wide variety of computer and industrial applications. They use an active element (normally a power transistor) operating in its linear region to generate the desired voltage. The output voltage is regulated by dropping excess input power in ohmic losses (heat) in a series dissipative component (resistor) or a transistor. Linear power supplies provide excellent regulation, very small ripple, and very little output noise. Switching power supplies use a switching element or regulator (normally a power transistor) to generate the desired voltage. They are also called switch-mode products or switching mode power supplies (SMPSs). These power supplies incorporate electronic components that continuously switch ON and OFF at a very high frequency. This switching action connects and disconnects energy-storing devices (inductors or capacitors) to and from the input source voltage or the output load. An SMPS design results in high power density (smaller size for the same power output) and reduced power consumption (higher efficiency) in comparison to linear power supplies. SCR power supplies use silicon-controlled rectifier (SCR) topology to provide well-regulated voltage and current output. Silicon-controlled rectifiers are four-layer thyristors with an input control terminal, an output terminal, and a cathode or terminal that is common to both the input and output terminals. An SCR circuit is commonly used in applications involving high voltages and currents.